Nowadays, the demand of high-speed data services on wireless bandwidth grows constantly, which has promoted various new technologies to be developed. For example, Device-to-Device (D2D) communication has been proposed to be an underlay to a cellular network so as to improve spectrum efficiency and system sum rate. The D2D communication is a new type of technology that allows user equipments (UEs) to communicate with each other through a direct connection instead of being relayed by a base station, and it is expected to become a key feature to be supported by next generation cellular networks. In the D2D communication, the D2D UEs could share the same subcarrier resources with conventional cellular UEs while the setup process will be still controlled by the network. As such, the D2D communication can provide a higher date rate, reduce power consumption, and lead to efficient resource (such as spectrum) utilization.
As an underlay to cellular systems, the D2D communication may share resources with cellular users in an either orthogonal or in a non-orthogonal manner. In an orthogonal sharing scheme, dedicated resources are allocated to D2D users. This scheme is easy to implement, but it can not fully exploit the potential of D2D communication to improve spectral efficiency of cellular systems. For this reason, the non-orthogonal sharing scheme has been also received much attention. In the non-orthogonal sharing scheme, the same resources are shared by the cellular users and the D2D users. However, due to resource sharing, the D2D communication may cause undesirable interference to the cellular users. Particularly, during the downlink (DL) transmission, the cellular users may suffer from interference from a D2D transmitter, and on the other hand, during the uplink (UL) transmission, a base station (BS) may be a victim of interference from the D2D transmitter. Therefore, in order to ensure that D2D communication is utilized efficiently, it usually requires employing appropriate resource sharing schemes with effective interference management.
Amongst others, optimizing resource sharing of the D2D communication underlaying cellular systems is of particular interest. For example, in paper “Resource sharing optimization for device-to-device communication underlaying cellular networks,” (C.-H. Yu, K. Doppler, C. B. Ribeiro, and O. Tirkkonen, IEEE Trans. Wireless Commun., vol. 10, no. 8, pp. 2752-2763, August 2011), there is disclosed a resource sharing optimization scheme. According to the scheme proposed in this paper, there are three resource allocation modes, i.e., a non-orthogonal sharing mode, an orthogonal sharing mode and a cellular mode. In the non-orthogonal sharing mode, D2D users and cellular users reuse the same resources, which may cause interferences to each other; in the orthogonal sharing mode, the D2D users are allocated part of the resources and the remaining part of resources is left to the cellular user for signal transmission; and in the cellular mode, the D2D users conventionally communicate with each other through the BS that acts as a relay node.
However, the schemes proposed by this paper are silent with the scenario of a multicell network or a coordinated system, e.g., conventional flattening multicell network, C-RAN, etc., where the D2D communication may share the spectra of multiple uplink cellular uses (CUs) in adjacent cells or Remote Radio Units (RRUs). Therefore, there is a need to find resource sharing schemes for D2D and cellular communications in the multicell network.